diff --git a/src/Tgstation.Server.Host/Controllers/InstanceController.cs b/src/Tgstation.Server.Host/Controllers/InstanceController.cs
index 22419b3be2..74c4d9b349 100644
--- a/src/Tgstation.Server.Host/Controllers/InstanceController.cs
+++ b/src/Tgstation.Server.Host/Controllers/InstanceController.cs
@@ -130,7 +130,14 @@ namespace Tgstation.Server.Host.Controllers
 			}, out var normalizedLocalPath);
 
 			if (rawPath.StartsWith(normalizedLocalPath, StringComparison.Ordinal))
-				return Conflict("Instances cannot be created in the installation directory!");
+			{
+				bool sameLength = rawPath.Length == normalizedLocalPath.Length;
+				char dirSeparatorChar = rawPath.ToCharArray()[normalizedLocalPath.Length];
+				if(sameLength
+					|| dirSeparatorChar == Path.DirectorySeparatorChar
+					|| dirSeparatorChar == Path.AltDirectorySeparatorChar)
+					return Conflict(new ErrorMessage { Message = "Instances cannot be created in the installation directory!" });
+			}
 
 			var dirExistsTask = ioManager.DirectoryExists(model.Path, cancellationToken);
 			bool attached = false;